Passenger car cargo covers of the type employing spring retraction rolls require mounting brackets for end caps accommodating roll removal when not in use. Open slots in such brackets have been found to involve a hazard when a roll comes loose during an accident with a potential for injuring occupants. Accordingly, certain vehicle manufacturers have required means for retaining the end caps which require manual release. Prior art constructions to meet such requirement include, as most relevant, a spring actuated slide which traps the end cap when installed in the bracket. The slide has a manually accessible projection which must be actuated to an open position both to install and to release the end cap. The slide in such bracket moves transversely to the end cap slot and the transverse motion of the slide requires a bracket depth exceeding that necessary for the slot per se which, in some cars, involves unavailable space. Furthermore, the requirement for manual release of the trapping element for installation adds inconvenience to reinstallation of the roll after removal.